U.S. patent application number 14/144357 was filed with the patent office on 2015-04-30 for method for controlling variable valve lift apparatus and variable valve lift system.
This patent application is currently assigned to Hyundai Motor Company. The applicant listed for this patent is Hyundai Motor Company. Invention is credited to Keun Sang KIM, Hyeungwoo LEE, Jang Su LEE, Jun YU.
Application Number | 20150114375 14/144357 |
Document ID | / |
Family ID | 52591555 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150114375 |
Kind Code |
A1 |
LEE; Jang Su ; et
al. |
April 30, 2015 |
METHOD FOR CONTROLLING VARIABLE VALVE LIFT APPARATUS AND VARIABLE
VALVE LIFT SYSTEM
Abstract
A method for controlling a variable valve lift apparatus
includes: measuring an operation mode switching condition;
determining whether the variable valve lift apparatus is in a
normal operation condition; controlling the operation of the
variable valve lift apparatus depending on a predetermined normal
valve lift switching map; determining whether the variable valve
lift apparatus is in a mode switching delay or switching disable
condition from a high lift mode to a low lift mode or whether the
variable valve lift apparatus is in the mode switching delay or
switching disable condition from the low lift mode to the high lift
mode; controlling the operation of the variable valve lift
apparatus depending on a predetermined low oil temperature valve
lift switching map; and controlling the operation of the variable
valve lift apparatus depending on a predetermined high oil
temperature valve lift switching map.
Inventors: |
LEE; Jang Su; (Yongin-si,
KR) ; YU; Jun; (Suwon-si, KR) ; KIM; Keun
Sang; (Anyang-si, KR) ; LEE; Hyeungwoo;
(Suwon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company |
Seoul |
|
KR |
|
|
Assignee: |
Hyundai Motor Company
Seoul
KR
|
Family ID: |
52591555 |
Appl. No.: |
14/144357 |
Filed: |
December 30, 2013 |
Current U.S.
Class: |
123/704 ;
123/90.1 |
Current CPC
Class: |
Y02T 10/42 20130101;
F02D 2200/023 20130101; Y02T 10/12 20130101; Y02T 10/18 20130101;
Y02T 10/40 20130101; F02D 2041/001 20130101; F02D 41/0002 20130101;
F01L 1/34 20130101; F02D 41/30 20130101; F02D 13/0207 20130101 |
Class at
Publication: |
123/704 ;
123/90.1 |
International
Class: |
F02D 13/02 20060101
F02D013/02; F02D 41/00 20060101 F02D041/00; F01L 1/34 20060101
F01L001/34; F02D 41/30 20060101 F02D041/30 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2013 |
KR |
10-2013-0127325 |
Claims
1. A method for controlling a variable valve lift apparatus,
comprising: measuring an operation mode switching condition of the
variable valve lift apparatus; determining, by a controller,
whether the variable valve lift apparatus is in a normal operation
condition based on the measured operation mode switching condition;
controlling, by the controller, operation of the variable valve
lift apparatus based on a predetermined normal valve lift switching
map if it is determined that the variable valve lift apparatus
satisfies the normal operation condition; determining, by the
controller, whether the variable valve lift apparatus is in a mode
switching delay or switching disable condition from a high lift
mode to a low lift mode or whether the variable valve lift
apparatus is in the mode switching delay or switching disable
condition from the low lift mode to the high lift mode, if it is
determined that the variable valve lift apparatus does not satisfy
the normal operation condition; controlling, by the controller, the
operation of the variable valve lift apparatus based on a
predetermined low oil temperature valve lift switching map when the
variable valve lift apparatus is in the mode switching delay or
switching disable condition from the high lift mode to the low lift
mode; and controlling, by the controller, the operation of the
variable valve lift apparatus depending on a predetermined high oil
temperature valve lift switching map when the variable valve lift
apparatus is in the mode switching delay or switching disable
condition from the low lift mode to the high lift mode.
2. The method of claim 1, wherein the low oil temperature valve
lift switching map includes a set first engine RPM which switches
the variable valve lift apparatus from the high lift mode to the
low lift mode depending on the measured operation mode switching
condition.
3. The method of claim 2, wherein the high oil temperature valve
lift switching map includes a set second engine RPM larger than the
first engine RPM which switches the variable valve lift apparatus
from the low lift mode to the high lift mode depending on the
measured operation mode switching condition.
4. The method of claim 1, further comprising: controlling, by the
controller, an air content control valve which controls an air
content introducing into the engine to increase the introducing air
content, when the variable valve lift apparatus is in the mode
switching delay or switching disable condition from the low lift
mode to the high lift mode.
5. The method of claim 1, further comprising: controlling, by the
controller, an injector to reduce an injected fuel amount, when the
variable valve lift apparatus is in the mode switching delay or
switching disable condition from the high lift mode to the low lift
mode.
6. The method of claim 1, wherein the operation mode switching
condition includes a set oil temperature condition and oil pressure
condition.
7. The method of claim 6, wherein the oil temperature is predicted
by measuring a cooling water temperature.
8. The method of claim 6, wherein the operation mode switching
condition further includes at least any one of atmospheric
temperature, atmospheric pressure, and atmospheric humidity.
9. A variable valve lift system, comprising: an engine including a
variable valve lift apparatus, an air content control valve that
controls an introducing air content, an engine RPM sensor, and an
injector; an oil pressure sensor configured to measure an oil
pressure to output a corresponding signal; a cooling water
temperature sensor configured to measure a cooling water
temperature to output a corresponding signal; a memory configured
to store a normal valve lift switching map which switches an
operation mode of the variable valve lift apparatus when the
variable valve lift apparatus is in a normal operation condition, a
low oil temperature valve lift switching map which switches the
operation mode of the variable valve lift apparatus when the
variable valve lift apparatus is in a mode switching delay or
switching disable condition from the high lift mode to the low lift
mode, and a high oil temperature valve lift switching map which
switches the operation mode of the variable valve lift apparatus
when the variable valve lift apparatus is in the mode switching
delay or switching disable condition from the low lift mode to the
high lift mode; and a controller configured to receive the
corresponding signal from the oil pressure sensor, the cooling
water temperature sensor, and the engine RPM sensor to determine
the currently available valve lift switching map among the valve
lift switching maps from the memory and control the operation of
the variable valve lift apparatus depending on the determined
corresponding valve lift switching map.
10. The method of claim 9, wherein the controller controls the
operation of the air content control valve to increase the air
content introducing into the engine when the variable valve lift
apparatus is controlled depending on the high oil temperature lift
switching map.
11. The method of claim 9, wherein the controller controls the
operation of the injector to reduce the fuel amount injected to the
engine when the variable valve lift apparatus is controlled
depending on the low oil temperature lift switching map.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority of Korean Patent
Application Number 10-2013-0127325 filed Oct. 24, 2013, the entire
contents of which application is incorporated herein for all
purposes by this reference.
BACKGROUND OF INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to a method for controlling a
variable valve lift apparatus and a variable valve lift system, and
more particularly, to a method for controlling a variable valve
lift apparatus depending on given conditions by determining whether
the variable valve lift apparatus is in a normal operation state
depending on the given conditions and a variable valve lift
system.
[0004] 2. Description of Related Art
[0005] An internal combustion engine combusts fuel and air supplied
to a combustion chamber to generate power.
[0006] When sucking air, an intake value is operated by driving a
camshaft and air is sucked in the combustion chamber while the
intake valve is opened.
[0007] Further, an exhaust valve is operated by driving the
camshaft and air is exhausted from the combustion chamber while the
exhaust valve is opened.
[0008] However, the optimal operation of the intake valve/exhaust
valve varies depending on a rotating speed of an engine.
[0009] That is, an appropriate lift or a valve opening/closing time
varies depending on the rotating speed of the engine.
[0010] Many researches to appropriately operate the valves
depending on the rotating speed of the engine as described above
have been conducted.
[0011] For example, research into a variable valve lift (VVL)
apparatus which operates the valve as another lift depending on an
engine RPM and a variable valve timing (VVT) apparatus which opens
and closes the valve at an appropriate timing depending on the
engine RPM has been conducted.
[0012] An oil control valve (OCV) which is used to operate the
variable valve lift operation controls an operation of the variable
valve lift apparatus by changing an oil passage. That is, the oil
control valve (OCV) changes the oil passage to change an oil
pressure transferred to the variable valve lift apparatus, thereby
operating the variable valve lift apparatus.
[0013] However, in the case of the control by the oil pressure, the
malfunction of the variable valve lift apparatus may occur
depending on a climatic condition, such that an operation range of
the variable valve lift apparatus may be reduced.
[0014] The reduction in the operation range of the variable valve
lift apparatus may lead to the deterioration of engine performance
and engine durability.
[0015] To solve the problems, an electric motor control scheme
independent of the oil pressure may be used. However, the electric
motor control scheme spends much cost and may increase power
consumption to increase fuel consumption.
[0016] The information disclosed in this Background section is only
for enhancement of understanding of the general background of the
invention and should not be taken as an acknowledgement or any form
of suggestion that this information forms the prior art already
known to a person skilled in the art.
BRIEF SUMMARY
[0017] Various aspects of the present invention have been made in
an effort to provide a method for controlling a variable valve lift
apparatus depending on given conditions by determining whether the
variable valve lift apparatus is in a normal operation state
depending on the given conditions, and a variable valve lift
system.
[0018] Various aspects of the present invention provide for a
method for controlling a variable valve lift apparatus, including:
measuring an operation mode switching condition of the variable
valve lift apparatus; determining, by a controller, whether the
variable valve lift apparatus is in a normal operation condition
based on the measured operation mode switching condition;
controlling, by the controller, the operation of the variable valve
lift apparatus depending on a predetermined normal valve lift
switching map if it is determined that the variable valve lift
apparatus satisfies the normal operation condition; determining, by
the controller, whether the variable valve lift apparatus is in a
mode switching delay or switching disable condition from a high
lift mode to a low lift mode or whether the variable valve lift
apparatus is in the mode switching delay or switching disable
condition from the low lift mode to the high lift mode, if it is
determined that the variable valve lift apparatus does not satisfy
the normal operation condition; controlling, by the controller, the
operation of the variable valve lift apparatus depending on a
predetermined low oil temperature valve lift switching map when the
variable valve lift apparatus is in the mode switching delay or
switching disable condition from the high lift mode to the low lift
mode; and controlling, by the controller, the operation of the
variable valve lift apparatus depending on a predetermined high oil
temperature valve lift switching map when the variable valve lift
apparatus is in the mode switching delay or switching disable
condition from the low lift mode to the high lift mode.
[0019] The low oil temperature valve lift switching map may include
a set first engine RPM which switches the variable valve lift
apparatus from the high lift mode to the low lift mode depending on
the measured operation mode switching condition.
[0020] The high oil temperature valve lift switching map may
include a set second engine RPM larger than the first engine RPM
which switches the variable valve lift apparatus from the low lift
mode to the high lift mode depending on the measured operation mode
switching condition.
[0021] The method for controlling a variable valve lift apparatus
may further include: controlling, by the controller, an air content
control valve which controls an air content introducing into the
engine to increase the introducing air content, when the variable
valve lift apparatus is in the mode switching delay or switching
disable condition from the low lift mode to the high lift mode.
[0022] The method for controlling a variable valve lift apparatus
may further include: controlling, by the controller, an injector to
reduce an injected fuel amount, when the variable valve lift
apparatus is in the mode switching delay or switching disable
condition from the high lift mode to the low lift mode.
[0023] The operation mode switching condition may include a
predetermined oil temperature condition and oil pressure
condition.
[0024] The oil temperature may be expected by measuring the cooling
water temperature.
[0025] The operation mode switching condition may further include
at least any one of atmospheric temperature, atmospheric pressure,
and atmospheric humidity.
[0026] Various aspects of the present invention provide for a
variable valve lift system, including: an engine configured to
include a variable valve lift apparatus, an air content control
valve which controls an introducing air content, an engine RPM
sensor, and an injector; an oil pressure sensor configured to
measure an oil pressure to output a corresponding signal; a cooling
water temperature sensor configured to measure a cooling water
temperature to output a corresponding signal; a memory configured
to store a normal valve lift switching map which switches an
operation mode of the variable valve lift apparatus when the
variable valve lift apparatus is in a normal operation condition, a
low oil temperature valve lift switching map which switches the
operation mode of the variable valve lift apparatus when the
variable valve lift apparatus is in a mode switching delay or
switching disable condition from the high lift mode to the low lift
mode, and a high oil temperature valve lift switching map which
switches the operation mode of the variable valve lift apparatus
when the variable valve lift apparatus is in the mode switching
delay or switching disable condition from the low lift mode to the
high lift mode; and a controller configured to receive the
corresponding signal from the oil pressure sensor, the cooling
water temperature sensor, and the engine RPM sensor to determine
the currently available valve lift switching map among the valve
lift switching maps from the memory and control the operation of
the variable valve lift apparatus depending on the determined
corresponding valve lift switching map.
[0027] The controller may control the operation of the air content
control valve to increase the air content introducing into the
engine when the variable valve lift apparatus is controlled
depending on the high oil temperature lift switching map.
[0028] The controller may control the operation of the injector to
reduce the fuel amount injected to the engine when the variable
valve lift apparatus is controlled depending on the low oil
temperature lift switching map.
[0029] According to the method for controlling a variable valve
lift apparatus and the variable valve lift system according to
various embodiments of the present invention, it is possible to
improve the operation limitation of the variable valve lift
apparatus by controlling the variable valve lift apparatus
depending on the given conditions by determining whether the
variable valve lift apparatus is in a normal operation state
depending on the given conditions.
[0030] The methods and apparatuses of the present invention have
other features and advantages which will be apparent from or are
set forth in more detail in the accompanying drawings, which are
incorporated herein, and the following Detailed Description, which
together serve to explain certain principles of the present
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a block diagram of an exemplary variable valve
lift system according to the present invention.
[0032] FIG. 2 is a flow chart of an exemplary method for
controlling a variable valve lift system according to the present
invention.
[0033] FIG. 3, FIG. 4 and FIG. 5 are graphs illustrating a valve
lift switching map of an exemplary method for controlling a
variable valve lift apparatus according to the present
invention.
[0034] FIG. 6 and FIG. 7 are graphs describing abnormal behaviors
of a general variable valve lift apparatus.
DETAILED DESCRIPTION
[0035] Reference will now be made in detail to various embodiments
of the present invention(s), examples of which are illustrated in
the accompanying drawings and described below. While the
invention(s) will be described in conjunction with exemplary
embodiments, it will be understood that present description is not
intended to limit the invention(s) to those exemplary embodiments.
On the contrary, the invention(s) is/are intended to cover not only
the exemplary embodiments, but also various alternatives,
modifications, equivalents and other embodiments, which may be
included within the spirit and scope of the invention as defined by
the appended claims.
[0036] Throughout the specification, unless explicitly described to
the contrary, the word "comprise" and variations such as
"comprises" or "comprising", will be understood to imply the
inclusion of stated elements but not the exclusion of any other
elements.
[0037] FIG. 1 is a block diagram of a variable valve lift system
according to various embodiments of the present invention.
[0038] Referring to FIG. 1, the variable valve lift system
according to various embodiments of the present invention includes
an engine 40, an oil pressure sensor 60, a cooling water
temperature sensor 70, a memory 50, and a controller 100.
[0039] The engine 40 may include a variable valve lift apparatus
10, an air content control valve 20 which controls an introducing
air content, an engine RPM sensor 80, and an injector 40.
[0040] In the variable valve lift system according to various
embodiments of the present invention, the air content control valve
20 may be a valve which directly controls a fresh air content
introducing into the engine 40 and may also be an EGR valve which
controls a ratio of the fresh air introducing into the engine 40 by
controlling an amount of EGR gas.
[0041] The variable valve lift apparatus 10 is a general variable
valve lift apparatus which implements a high lift mode and a low
lift mode based on an oil pressure. That is, when a high pressure
oil is supplied to the variable valve lift apparatus 10, the
variable valve lift apparatus 10 is operated in the high lift mode
and when a low pressure oil is supplied to the variable valve lift
apparatus 10 and the oil supplied to the variable valve lift
apparatus 10 is reliefed, the variable valve lift apparatus 10 is
operated in the low lift mode.
[0042] The oil pressure sensor 60 measures the oil pressure, in
particular, the oil pressure operating the variable valve lift
apparatus 10 to output the corresponding signal.
[0043] The cooling water temperature sensor 70 measures a cooling
water temperature to output the corresponding signal.
[0044] The memory 50 stores a normal valve lift switching map which
switches an operation mode of the variable valve lift apparatus 10
when the variable valve lift apparatus 10 is in a normal operation
condition, a low oil temperature valve lift switching map which
switches the operation mode of the variable valve lift apparatus 10
when the variable valve lift apparatus 10 is in a mode switching
delay or switching disable condition from the high lift mode to the
low lift mode, and a high oil temperature valve lift switching map
which switches the operation mode of the variable valve lift
apparatus 10 when the variable valve lift apparatus 10 is in the
mode switching delay or switching disable condition from the low
lift mode to the high lift mode.
[0045] The controller 100 receives the corresponding signal from
the oil pressure sensor 60, the cooling water temperature sensor
70, and the engine speed sensor 80 to determine the currently
available valve lift switching map among the valve lift switching
maps from the memory 50, and controls the operation of the variable
valve lift apparatus 10 depending on the determined corresponding
valve lift switching map.
[0046] FIG. 2 is a flow chart of a method for controlling a
variable valve lift system according to various embodiments of the
present invention.
[0047] Referring to FIGS. 1 and 2, the method for controlling a
variable valve lift apparatus according to various embodiments of
the present invention includes: measuring an operation mode
switching condition of the variable valve lift apparatus 10 (S10);
determining whether the controller 100 is the normal operation
condition of the variable valve lift apparatus 10 based on the
measured operation mode switching condition (S20); controlling, by
the controller 100, the operation of the variable valve lift
apparatus 10 depending on the predetermined normal valve lift
switching map if it is determined that the controller 100 satisfies
the normal operation condition (S30); determining whether the
variable valve lift apparatus 10 is in the mode switching delay or
switching disable condition from the high lift mode to the low lift
mode or determining whether the variable valve lift apparatus is in
the mode switching delay or switching disable condition from the
low lift mode to the high lift mode if it is determined that the
controller 100 does not satisfy the normal operation condition
(S60); controlling, by the controller 100, the operation of the
variable valve lift apparatus 10 depending on the predetermined low
oil temperature valve lift switching map when the variable valve
lift apparatus 10 is in the mode switching delay or switching
disable condition from the high lift mode to the low lift mode
(S70); and controlling, by the controller 100, the operation of the
variable valve lift apparatus 10 depending on the predetermined
high oil temperature valve lift switching map when the variable
valve lift apparatus 10 is in the mode switching delay or switching
disable condition from the low lift mode to the high lift mode
(S90).
[0048] After the step S30, the lift switching signal is output
(S40) and the operation mode of the valve lift is switched (S50),
depending on the normal valve lift switching map.
[0049] The operation mode switching condition may include a
predetermined oil temperature condition and oil pressure
condition.
[0050] The oil temperature may be expected by measuring the cooling
water temperature.
[0051] That is, the oil temperature may directly be measured by
using the oil temperature sensor 70 and may expect the oil
temperature using the relationship between the cooling water
temperature and the oil temperature by an experiment. A method for
predicting the oil temperature using the cooling water temperature
is apparent to a person having ordinary skill in the art, and
therefore the detailed description thereof will be omitted.
[0052] In the step S20, the normal operation condition of the
variable valve lift apparatus 10 may be a condition including the
predetermined oil pressure and oil pressure set by the experiment
at which the variable valve lift apparatus 10 may be normally
operated.
[0053] The low oil temperature valve lift switching map may include
a set first engine RPM which switches the variable valve lift
apparatus 10 from a high lift mode to a low lift mode depending on
the measured operation mode switching condition.
[0054] The high oil temperature valve lift switching map may
include a set second engine RPM larger than the first engine RPM
which switches the variable valve lift apparatus 10 from the high
lift mode to the low lift mode depending on the measured operation
mode switching condition.
[0055] In the step S60, the abnormal operation condition, the mode
switching delay, or the switching disable condition, which is a
condition including the oil pressure and oil temperature set by the
experiment at which the variable valve lift apparatus 10 may not be
normally operated, determines whether the variable valve lift
apparatus 10 is in the state in which the variable valve lift
apparatus 10 may not be normally switched from the high lift mode
to the low lift mode or whether the variable valve lift apparatus
10 is in the state in which the variable valve lift apparatus 10
may not be normally switched from the low lift mode to the high
lift mode.
[0056] The method for controlling a variable valve lift apparatus
according to various embodiments of the present invention may
further include controlling the introducing air content by
controlling, by the controller 100, the operation of the air
content control valve 20 when the variable valve lift apparatus 10
is in the mode switching delay or switching disable condition from
the low lift mode to the high lift mode (S100). For example, the
method copes with the switching delay or switching disabling of the
lift mode by increasing the introducing air content.
[0057] The method for controlling a variable valve lift apparatus
according to various embodiments of the present invention may
further include reducing the injected fuel amount by controlling,
by the controller 100, the injector 30 when the variable valve lift
apparatus 10 is in the mode switching delay or switching disable
condition from the high lift mode to the low lift mode (S80).
[0058] The operation mode switching condition may further include
at least any one of atmospheric temperature, atmospheric pressure,
and atmospheric humidity.
[0059] FIGS. 6 and 7 are graphs describing abnormal behaviors of a
general variable valve lift apparatus.
[0060] When the oil temperature is a low temperature and the oil
pressure is a high pressure, the graph illustrated in FIG. 6
illustrates that the switching from the high lift mode to the low
lift mode of the variable valve lift apparatus is delayed.
[0061] For example, when the oil temperature is 10.degree. C. or
less and the oil pressure is 5 bar or more, the viscosity of oil is
relatively increased and thus the dissolution of the oil supplied
to the variable valve lift apparatus 10 is delayed, such that the
switching from the high lift mode to the low lift mode of the
variable valve lift apparatus may be in a condition in which the
switching of the high lift mode of the variable valve lift
apparatus into the low lift mode thereof is delayed or disabled and
the incomplete combustion of fuel may occur.
[0062] When the oil temperature is a high temperature and the oil
pressure is a low pressure, the graph illustrated in FIG. 7
illustrates that the switching from the low lift mode to the high
lift mode of the variable valve lift apparatus is disabled.
[0063] For example, when the oil temperature is 120.degree. C. or
more and the oil pressure is 1 bar or less, the viscosity of oil is
relatively low and thus the switching of the variable value lift
apparatus from the low lift mode to the high lift mode may be in a
condition in which the switching of the low lift mode of the
variable valve lift apparatus to the high lift mode thereof Is
delayed or disabled, such that the exhaust gas temperature may be
excessively increased.
[0064] As such, in the case of the general variable valve lift
apparatus, the malfunction of the variable valve lift apparatus may
occur depending on the given conditions, such that the operation
range of the variable valve lift apparatus may be reduced.
[0065] The reduction in the operation range of the variable valve
lift apparatus may lead to the deterioration of engine performance
and engine durability.
[0066] However, the method for controlling a variable valve lift
apparatus according to various embodiments of the present invention
may improve the operation limitation of the variable valve lift
apparatus by changing the switching condition of the valve lift in
the condition in which the abnormal behavior of the variable valve
lift apparatus occurs.
[0067] FIGS. 3 to 5 are graphs illustrating a valve lift switching
map of the method for controlling a variable valve lift apparatus
according to various embodiments of the present invention.
[0068] FIG. 5 is a graph illustrating the valve lift switching map
according to the method for controlling a variable valve lift
apparatus according to various embodiments of the present invention
in the condition of the oil temperature and the oil pressure at
which the variable valve lift apparatus may be normally
operated.
[0069] As illustrated in FIG. 5, in the condition of the oil
temperature and the oil pressure at which the variable valve lift
apparatus may be normally operated, the switching map between the
low lift mode and the high lift mode is set depending on an engine
load and the engine RPM, which may be determined by the
experiment.
[0070] FIGS. 3 and 4 are diagrams illustrating each of the high oil
temperature valve lift switching map and the low oil temperature
valve lift switching map according to the method for controlling a
variable valve lift apparatus according to various embodiments of
the present invention.
[0071] As illustrated in FIG. 4, when the oil temperature is a low
temperature and the oil pressure is a high pressure, a control to
keep the high lift mode in an area of the set first engine RPM or
more is performed, in which the set first engine RPM may be
determined by the experiment.
[0072] For example, when the oil temperature is 10.degree. C. or
less and the oil pressure is 5 bar or more, the switching of the
variable valve lift apparatus from the high lift mode to the low
lift mode is delayed or disabled, such that the operation area of
the high lift mode may be kept.
[0073] In this case, since a required output of the engine is low
but the operation mode of the engine 40 is the high lift mode, the
injector 30 is controlled in some section to reduce the supplied
fuel amount.
[0074] As illustrated in FIG. 3, when the oil temperature is a high
temperature and the oil pressure is a low pressure, a control to
keep the low lift mode in an area of the set second engine RPM or
less is performed, in which the set second engine RPM may be
determined by the experiment.
[0075] For example, when the oil temperature is 120.degree. C. or
more and the oil pressure is 1 bar or less, the viscosity of oil is
relatively low and thus the switching of the variable value lift
apparatus from the low lift mode to the high lift mode may be in a
condition in which the switching of the low lift mode of the
variable valve lift apparatus to the high lift mode thereof is
disabled or delayed, such that the operation range of the low lift
mode may be kept.
[0076] In this case, since the required output of the engine is
high but the operation mode of the engine 40 is the low lift mode,
the supplied air content may be increased, for example, the EGR
valve open degree is reduced to be able to increase the supplied
fresh air content.
[0077] The operation mode switching condition may further include
at least any one of the atmospheric temperature, the atmospheric
pressure, and the atmospheric humidity, which is included in the
high oil temperature valve lift switching map and the low oil
temperature valve lift switching map to be applied to the control
of the variable valve lift apparatus.
[0078] For example, when the atmospheric temperature is -7.degree.
C. or less, the switching from the high lift mode to the low lift
mode may be delayed or disabled and when the atmospheric
temperature is 40.degree. C. or more, the switching from the low
lift mode to the high lift mode may be delayed or disabled.
[0079] Further, the atmospheric pressure and the humidity may also
affect the switching between the high lift mode and the low lift
mode, which may reflect the value determined by the experiment on
the map.
[0080] In the above description, the maps may be defined by
reflecting appropriate values of the oil temperature, the oil
pressure, the atmospheric temperature, the atmospheric pressure,
the atmospheric humidity, and the like by the experiment depending
on a kind of used oil. Therefore, in the method for controlling a
variable valve lift apparatus according to various embodiments of
the present invention and the variable valve lift system, the
values thereof are not limited to any specific value.
[0081] The graphs of FIGS. 3 to 7 are simply illustrated to help
the convenience of understanding, but are simplified to indicate
one tendency, in which it is apparent that the lift switching map
applied to the method for controlling a variable valve lift
apparatus and the variable valve lift system according to various
embodiments of the present invention may use various forms of
graphs depending on the oil temperature, the oil pressure, the
atmospheric temperature, and the like.
[0082] In addition, the first engine RPM which is a reference to
switch the operation mode of the variable valve lift apparatus 10
and the second engine RPM larger than the first engine RPM may have
various numerical values depending on the oil temperature, the oil
pressure, the atmospheric temperature, and the like, not on the
specified one RPM.
[0083] According to the method for controlling a variable valve
lift apparatus and the variable valve lift system according to
various embodiments of the present invention, the second engine RPM
has the engine RPM larger than the first engine RPM to keep the
current operation mode of the variable valve lift apparatus in the
mode switching delay or the switching disable condition, thereby
protecting the engine and preventing the reduction in vehicle
performance.
[0084] According to the method for controlling a variable valve
lift apparatus and the variable valve lift system according to
various embodiments of the present invention, it is possible to
improve the operation limitation of the variable valve lift
apparatus by controlling the variable valve lift apparatus
depending on the given conditions by determining whether the
variable valve lift apparatus is in a normal operation state
depending on the given conditions.
[0085] The foregoing descriptions of specific exemplary embodiments
of the present invention have been presented for purposes of
illustration and description. They are not intended to be
exhaustive or to limit the invention to the precise forms
disclosed, and obviously many modifications and variations are
possible in light of the above teachings. The exemplary embodiments
were chosen and described in order to explain certain principles of
the invention and their practical application, to thereby enable
others skilled in the art to make and utilize various exemplary
embodiments of the present invention, as well as various
alternatives and modifications thereof. It is intended that the
scope of the invention be defined by the Claims appended hereto and
their equivalents.
* * * * *